9/18/2019

Introduction

Why have a survey design?

This type of survey can be useful for the discovery of zebra mussels

Transect sampling is one approach to cover area quickly

A formal design controls effort and area surveyed so we can estimate density.

Methods

Three survey designs to explore sampling tradeoffs

Estimating detection with two observers

  • First observer marks each detected cluster
  • Second observer looks for new clusters
  • New detections inform our estimate of detection probability

Using the additional information from distance surveys

We compared designs across densities


Main Findings

Detection probability estimates




  • Detection estimates were consistent between lakes
  • In transect surveys the detection probability by either observer detecting the zebra mussel was > 90%.
  • In distance surveys detection probability by either observer was around 50%

Density estimates

  • Estimates from transect surveys were consistently low
  • Variance of Quadrat estimates was highest at low to medium density

Recommendations



  • Apply distance surveys with two divers at low to moderate densities
  • Quadrat surveys at high densities

Other resources

Acknowledgements

Jake Ferguson

Michael McCartney

Naomi Blinick

Leslie Schroeder

Sarah Baker

Aislyn Keyes

Austin Hilding

Kylie Cattoor

Keegan Lund